Solar Projector

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Solar Projector:   This isn’t anything I invented but in all modesty it is the lightest, safest, best image in any solar projector in a 4 inch size bar none.  It is simply a plano-convex lens with a very long focal length (80+ feet) which gives it a large image scale and freedom from color aberration.  It’s absolutely safe because the image is never concentrated to cause burns.  It is fed by an optical flat and mounts on a camera tripod weighing only 2.2 lbs..  It’s 8 inch diameter solar image is by far the best for group viewing of the sun.  Check my yard sale for availability.  There is no better solar projector for public viewing an eclipse.

sun10

opticsed@gmail.com

Check out my You-Tube video https://www.youtube.com/watch?v=pgQOsK6RdC4

Tracking

A little late I wondered if I could add tracking to my existing solar projector.  I had done this once before by making a special tilting mount.  However I realized I can rotate my projector around a horizontal axis as shown below with the head on my tripod.   If the

rotate2

sun is perpendicular to the plane of my base board (blue arrows) then a simple tangent arm drive could rotate the mirror keeping the sun on the screen.  Well even though there is a tangent error with a tangent arm and the sun’s track is not really straight it should work well enough to keep it on the screen for a considerable length of time so that I don’t have to keep repositioning the mirror so often.  Well it worked very nicely and I should have done it sooner.

Here is better shot.  A DC gearmotor drives a 6-32 threaded rod and drives a delrin curved split nut kept in contact with a spring.  The 5 rpm motor was too fast and a simple PWM board didn’t slow it enough so I needed a bit more speed reduction circuitry.

tester

I’m thinking of building more solar projectors with this feature.